The present invention generally relates to a suspension assembly for a disk drive, and more particularly to a flex suspension assembly having a flex cable attached to a suspension assembly for transmitting electrical signals between a transducer and control circuitry in the disk drive.
A hard disk drive includes a suspension assembly for supporting a transducer head relative to a rotating magnetic disk. The transducer head includes a slider supporting at least one transducer, such as an inductive transducer, a magnetoresistance (MR) transducer, or giant magnetoresistance (GMR) transducer. The transducer head can include separate read and write transducers or one read/write transducer. The transducer communicates with the disk surface to write data to and read data from the disk.
The suspension assembly includes a flexure or gimble connecting the slider to the suspension assembly. The flexure resiliently supports the slider and allows the slider to move vertically and to pitch and roll about a pivot while the slider follows the topography of the rotating disk. The slider includes a hydrodynamic air bearing to receive a lifting force from air movement resulting from rotation of the disk. The flexure is rigid in the in-plane directions for maintaining precise in-plane positioning.
The suspension assembly also includes a load beam which acts as a spring supplying a downward force on the transducer head to counteract the hydrodynamic lifting force developed by the air bearing. The load beam is attached to a rigid support arm of an actuator arm. The load beam is typically connected to the support arm by a well-known technique referred to as swaging or ball staking. The load beam is resilient in the vertical direction. The vertical resiliency permits the slider to follow the topography of the disk surface. As with the flexure, the load beam is rigid in the in-plane directions.
Electrical signals are transmitted between control circuitry in the disk drive and the transducer via small conductors. These conductors are typically twisted copper wires or copper traces enclosed in a flex cable. There are typically two conductors, but the number of conductors may vary. In conventional suspension assembly designs, where the suspension assembly employs flex cables, the flex cable is typically attached to the suspension assembly with a structural rigid adhesive, such as a liquid ultra-violet (UV) cure adhesive or a pressure sensitive adhesive.
The suspension assembly including the load beam and flexure; the conductors; and the transducer head including the slider and the transducer together form a head-gimble assembly (HGA).
The suspension assembly""s load beam and flexure are typically made from stainless steel. The load beam includes flanges along the sides of the load beam to stiffen the load beam and to raise the resonance frequencies for its first torsion vibration mode and its second torsion vibration mode.
Dampening of the first torsion and second torsion vibration mode gain is typically achieved by the application of a constrained layer dampener. The constrained layer dampener typically comes in the form of a pressure sensitive adhesive on a silicon release liner. The constrained layer dampener is applied by applying pressure and elevating temperature and removing the release liner. The constrained layer dampener is problematic because it is an extra component being added to a suspension assembly in a very cost-competitive hard disk drive market. In addition, the added manufacturing steps to apply the constrained layer dampener with the pressure sensitive adhesive further increase the cost of the disk drive. Moreover, the constrained layer dampeners are typically not as clean as would be desirable, which can cause, among other things, outgassing problems.
For the reasons stated above, a suspension assembly is desired which adequately dampens the first torsion vibration mode and the second torsion vibration mode gains without using a constrained layer dampener.
The present invention provides a flex suspension assembly attachable to an actuator arm in a disk drive. The flex suspension assembly includes a suspension assembly and a flex cable. The suspension assembly is adapted to resiliently support a transducer head in the disk drive. The flex cable has a flexible sleeve and conductors disposed in top of the flexible sleeve adapted to provide a path for electrical signals transmitted to and from the transducer head. A dampening adhesive is applied between the flex cable and the suspension assembly in at least one dampening adhesive area defined by dampening adhesive control features that bound continuous contact between the flex cable and the suspension assembly. The dampening adhesive has a low modulus of elasticity to provide structural dampening to the flex suspension assembly.
In one embodiment, a structural adhesive is applied between the flex cable and the suspension assembly in at least one structural adhesive area defined by structural adhesive control features that bound continuous contact between the flex cable and the suspension assembly. The structural adhesive has a high modulus of elasticity to provide at least one rigid joint between the flex cable and the suspension assembly in the at least one structural adhesive area.
In one embodiment, the suspension assembly includes a base plate adapted to attach to the actuator arm in the disk drive, a load beam attached to the base plate, and a flexure attached to the load beam and adapted to resiliently support the transducer head.
In one embodiment, the at least one dampening adhesive area is located between the flex cable and the load beam. In one embodiment, a structural adhesive is applied between the flex cable and the flexure in at least one structural adhesive area defined by structural adhesive control features that bound continuous contact between the flex cable and flexure. In one embodiment, the load beam includes a tail tack tab and a structural adhesive is applied between the flex cable and tail tack tab in at least one structural adhesive area defined by structural adhesive control features that bound continuous contact between the flex cable and tail tack tab.
In one embodiment, the flex suspension assembly the dampening adhesive provides structural dampening to the flex suspension assembly in high strain areas.
In one embodiment, the dampening adhesive has a modulus of elasticity in a range from approximately 100,000 pounds per square inch (psi) to approximately 1,000,000 psi. In one embodiment, the structural adhesive has a modulus of elasticity in a range from approximately 1.5 million pounds per square inch (psi) to approximately 2.5 million psi.
One aspect of the present invention provides a method of forming a flex suspension assembly which is attachable to an actuator arm in a disk drive. The method includes providing a suspension assembly adapted to resiliently support a transducer head in the disk drive. The method also includes providing a flex cable having a flexible sleeve and conductors disposed in top of the flexible sleeve adapted to provide a path for electrical signals transmitted to and from the transducer head. The method also includes applying a dampening adhesive between the flex cable and the suspension assembly in at least one dampening adhesive area defined by dampening adhesive control features that bound continuous contact between the flex cable and the suspension assembly. The dampening adhesive having a low modulus of elasticity to provide structural dampening to the flex suspension assembly.
In one embodiment, the dampening adhesive provides structural dampening to the flex suspension assembly to significantly reduce a first torsion vibration mode gain of the flex suspension assembly. In one embodiment, the dampening adhesive provides structural dampening to the flex suspension assembly to significantly reduce a second torsion vibration mode gain of the flex suspension assembly. In these embodiments, the dampening adhesive emulates a conventional constrained layer dampener without actually having a constrained layer dampener added to the flex suspension assembly. The dampening adhesive can provide dampening which is particularly beneficial in disk drives, because a position control system of the disk drive must quickly locate the transducer head above a correct data track and maintain that positioning during operation. Accordingly, one embodiment of a disk drive employing a flex suspension assembly according to the present invention requires minimal first torsion vibration mode gain and second torsion vibration mode gain in the suspension assembly.